Whenever I provision a new Google Cloud project, I always get bitten by this error. I keep forgetting to set up IAM rules to allow Cloud Build access to App Engine.
Operation completed over 1 objects/8.6 KiB. BUILD Already have image (with digest): gcr.io/cloud-builders/gcloud ERROR: (gcloud.app.deploy) User [USER_ID_REDACTED@cloudbuild.gserviceaccount.com] does not have permission to access app [APP_ID_REDACTED] (or it may not exist): The caller does not have permission ERROR ERROR: build step 0 "gcr.io/cloud-builders/gcloud" failed: exit status 1
To fix this, go into Settings under Cloud Build and enable access to App Engine, and any other cloud service you use in conjunction with Cloud Build. Then wait a moment for the settings to take effect and rerun the build.